I do not know if it is variant or the tightest (because there is always more than one leg) version of "leg on the ground". It could also be a twist for the expression "having your feet on the ground".
In Costa Rica it is used to refer to a humble person, of scarce economic resources.
Have very clear ideas. Be landed. Realistic. Someone who is never, castles in the air
It could be a colloquial expression to indicate that someone is barefoot: " that child likes to be with the feet on the ground! "